One possibility for the design of surgical lamps are so-called single reflector lamps. In such lamps, the light source is a halogen lamp or a gas discharge lamp, which is arranged in the focal point of a large reflector having a diameter of about 500 mm to 1000 mm. By displacing the light source along the central axis of the reflector more or less out of the optimum focal point or into the optimum focal point, the diameter of the light field, i.e., the illuminated diameter in the operating field is enlarged or narrowed and the focal point is shifted, i.e., the distance between the location which is illuminated as the brightest where the reflected light beams intersect and the lamp body of the surgical lamp is modified along a central axis of the lamp body. Thereby, a complex mechanism which allows a reliable and smooth-running operation without any big effort of operation for the operator is necessary.
Multi-reflector lamps constitute another construction. Multi-reflector lamps typically include a central spotlight or a central light module, which is rigidly fixed to the lamp body, and several spotlights or light modules, which are annularly arranged about the central spotlight or the central light module. A change of direction of the light emitted by the outer spotlights or light modules is achieved by radially pivotable illuminants or reflectors, or the spotlights or light modules themselves are radially pivotably adjustable so that the distance between the focal point of the light beams of the outer spotlights or light modules changes and the lamp body along the central axis changes. A complex mechanism for synchronously reliably adjusting of the outer illuminants, reflectors or light modules is necessary for such multi-reflector lamps.
Other kinds of surgical lamps are designed without any adjustability of the light field diameter or of the position of the focal point along the central axis. In such lamps, the light characteristics, diameter of the light field and focal point are optimally adjusted for one operating point. A modification of the light field diameter is generally only possible by varying the distance between the lamp body and the operation field. Varying the distance of the focal point is not generally possible. When using multi-reflector lamps, there is a risk that the light field seems no longer homogenous but several light points are projected in the operation area when the distance between the lamp body and the operation site is small.